Navigation system user terminal navigation device and information recording method

ABSTRACT

A navigation system includes a controller that compresses at least one of a plurality of information portions, each one of the plurality of information portions having a priority, wherein each of the at least one of the plurality of information portions is compressed based on its priority; and a transmitter that transmits the at least one compressed information portion to a navigation device. A navigation device includes a receiver that receives at least one of a plurality of information portions, each one of the plurality of information portions having a priority, wherein each of the at least one of the plurality of information portions is compressed based on its priority.

INCORPORATION BY REFERENCE

This application is a national stage of International Patent ApplicationPCT/JP2003/007911, filed Jun. 23, 2003, which claims priority ofJapanese Patent Application No. 2002-182134 filed Jun. 21, 2002. Thedisclosures of which, including the specification, drawings, and claimsare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a navigation system, user terminal,navigation device, and information recording method.

2. Description of Related Art

In a conventional navigation device, a current position of a vehicle isdetected by means of GPS (global positioning system). At the same time,a vehicle direction is detected based on the vehicle's angular velocitydetected by a gyro sensor. A map screen is formed on a display of adisplay section. A current position, a surrounding map, and the vehicledirection are indicated on the map screen. Therefore, an operator, candrive a vehicle following the current position, surrounding map and thevehicle direction indicated on the map screen.

If the driver sets a target destination and a search condition, a routefrom the current position up to the target destination is searched forbased on the search condition. Then, the searched route is displayed ona search route display screen formed on the display or audibly output byan audio output section communicate. Therefore, the driver can drive avehicle along the searched route.

The navigation device includes a communication section, and is capableof receiving traffic information, for example, congestion informationthrough the communication section and displaying the received congestioninformation on the map screen.

A navigation system has been proposed in which the user transmits routeguidance data to the navigation device before the user operates thevehicle. When the user operates the vehicle and starts driving, theroute guidance can start following the transmission of the routeguidance data (see Japanese Patent Application Laid-Open No. HEI6-243395). In this case, the route guidance data is obtained byoperating a personal computer at a home or in an office to input, forexample, a target destination and/or search condition and route guidancedata is transmitted to the navigation device while the vehicle isparked.

However, according to this conventional navigation device, if a timenecessary for transmitting the route guidance data to the navigationdevice (hereinafter referred to as “required communication time”) islong, the navigation device needs to be turned on during that period.Therefore, electric power consumed by the navigation device is increasedand a load applied to a battery mounted on the vehicle is increasedtremendously.

SUMMARY OF THE INVENTION

Accordingly, various exemplary embodiments of this invention provide anavigation system, including a controller that compresses at least oneof a plurality of information portions, each one of the plurality ofinformation portions having a priority, wherein each of the at least oneof the plurality of information portions is compressed based on itspriority; and a transmitter that transmits the at least one compressedinformation portion to a navigation device.

Various exemplary embodiments of the invention provide a navigationdevice, including a receiver that receives at least one of a pluralityof information portions, each one of the plurality of informationportions having a priority, wherein each of the at least one of theplurality of information portions is compressed based on its priority.

Various exemplary embodiments of the invention provide a method fortransmitting information to a navigation device, including compressingat least one of a plurality of information portions, each one of theplurality of information portions having a priority, wherein each of theat least one of the plurality of information portions is compressedbased on its priority; and transmitting the at least one compressedinformation portion to a navigation device.

Various exemplary embodiments of the invention provide a method forreceiving information in a navigation device, including receiving atleast one of a plurality of information portions, each one of theplurality of information portions having a priority, wherein each of theat least one of the plurality of information portions is compressedbased on its priority.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described withreference to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a navigation system according to a firstexemplary embodiment of the invention;

FIG. 2 is a diagram for explaining a navigation device according to thefirst exemplary embodiment of the invention;

FIG. 3 is a flow chart indicating the operation of a personal computeraccording to the first exemplary embodiment of the invention;

FIG. 4 is a diagram showing the sub-routine of compression processingaccording to the first exemplary embodiment of the invention;

FIG. 5 is a flow chart showing the operation of the navigation deviceaccording to the first exemplary embodiment of the invention;

FIG. 6 is a diagram showing the data configuration of compressed dataaccording to the first exemplary embodiment of the invention;

FIG. 7 is a diagram showing data configuration upon decompressionprocessing according to the first exemplary embodiment of the invention;

FIG. 8 is a flow chart showing the operation of a personal computeraccording to a second exemplary embodiment of the invention;

FIG. 9 is a flow chart showing the operation of a personal computeraccording to a third exemplary embodiment of the invention;

FIG. 10 is a diagram showing the sub-routine of partial compressionprocessing according to the third exemplary embodiment of the invention;

FIG. 11 is a main flow chart showing the operation of a navigationdevice according to the third exemplary embodiment of the invention;

FIG. 12 is a diagram showing the sub-routine of decompression processingaccording to the third exemplary embodiment of the invention;

FIG. 13 is a main flow chart showing the operation of a personalcomputer according to a fourth exemplary embodiment of the invention;

FIG. 14 is a main flow chart showing the operation of a navigationdevice according to a fifth exemplary embodiment of the invention;

FIG. 15 is a main flow chart showing the operation of a navigationdevice according to a sixth exemplary embodiment of the invention;

FIG. 16 is a diagram showing the sub-routine of compression processingaccording to a seventh exemplary embodiment of the invention;

FIG. 17 is a flow chart showing the operation of the navigation deviceaccording to the seventh exemplary embodiment of the invention;

FIG. 18 is a diagram showing the data configuration of compressed dataaccording to the seventh exemplary embodiment of the invention;

FIG. 19 is a diagram showing the data configuration upon decompressionprocessing of surrounding data according to the seventh exemplaryembodiment of the invention;

FIG. 20 is a diagram showing the sub-routine of a partial compressionprocessing according to an eighth exemplary embodiment of the invention;

FIG. 21 is a flow chart showing the operation of the navigation deviceaccording to the eighth exemplary embodiment of the invention;

FIG. 22 is a main flow chart showing the operation of a personalcomputer according to a ninth exemplary embodiment of the invention;

FIG. 23 is a diagram showing the sub-routine of compression processingaccording to the ninth exemplary embodiment of the invention; and

FIG. 24 is a diagram showing the data configuration upon decompressionprocessing according to the ninth exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 is a block diagram of a navigation system according to a firstexemplary embodiment of the invention. As shown in FIG. 1, thenavigation system includes a personal computer 61 as a user terminal andan information center 62 as an information provider. The personalcomputer 61, the information center 62 and the like are connected via anetwork 43. The information center 62 provides navigation data.

The navigation system includes a navigation device 14 which may be avehicle on-board device mounted on a vehicle. The navigation device 14may include a navigation processing section 17, a data recording section16 as an information recording section, a communication section 38.

The personal computer 61 may include a CPU 71 as an arithmetic operationunit and control unit, a display section 72 for notifying an operator ofvariety of information, an operating section 73, a recording section 74,a communication section 75. The communication section 75 may contain,for example, a modem (not shown) for connecting the personal computer 61to the information center 62, and/or an access point (not shown) forconnecting the personal computer 61 to the navigation device 14 via thecommunication section 38 by means of radio.

Although according to this embodiment, the CPU 71 is used as thearithmetic operation unit and control unit, an MPU or the like may beused instead of the CPU 71. The display section 72 may include, forexample, a CRT display, a liquid crystal display, and/or a plasmadisplay. Although according to this exemplary embodiment, the displaysection 72 visually communicates with a user, an audio unit whichnotifies the operator of variety of information audibly may be usedinstead of the display section 72.

The operation section 73 may include, for example, a keyboard, a mouse,and the like. Alternatively, a touch panel formed on the above mentioneddisplay may be used. Operational regions such as various kinds of keys,switches, buttons and the like may be formed on the display on the touchpanel. Further, the operation section may include a bar code reader, aremote control unit for remote control operation, a joy stick, alight-pen, a stylus pen, or the like.

The recording section 74 may include such internal storage units as aRAM, a ROM, a flash memory, and/or a hard disk. The recording section 74may also include a flexible disc, a magnetic tape, a magnetic drum, aCD-ROM, a CD-R, a MD, a DVD, an optical disc, a MO, a IC card, anoptical card, a memory card, or the like.

Although, according to this exemplary embodiment, the personal computer61 is used as the user terminal, any other device which can be connectedto the network 43 and execute bi-directional communication, such as anelectronic notebook, a portable phone, a portable terminal, a PDA(personal portable information terminal), a TV phone, a game machine, orthe like may be used instead of the personal computer 61.

The information center 62 can include a server 63, a navigation database(DB) 64 which is connected to the server 63 and stores navigation data,and the like. The navigation database 64 may include map data fordisplaying a map, a search data for searching for a route, a facilitydata on various kinds of facilities, and the like. Data such as roaddata, intersection data, node data may be included in the map data.

The road data may include data representing road width, gradient, cant,bank, road condition, number of lanes, a location in which the number oflanes decreases, a location in which the road width decreases, railroadcrossings, and the like. Specifically, with respect to corners, the roaddata may include data representing curvature radius, intersection,T-shaped crossing, corner entrance/exit, and the like. The road data mayfurther include data representing a descending road, an ascending road,and the like. With respect to the road type, the road data may includedata representing general roads, national roads, prefectural roads,narrow streets, highway/toll express roads, urban express roads, and/ortoll roads. The road data may include data representing a road attachedto an entrance/exit (ramp way), and/or data recording toll booths andthe like.

The node data may include data representing a branch point (includingintersection, T-shaped crossing and the like) of an actual road,coordinates (position) of a node point set at every predetermineddistance corresponding to the curvature radius or the like of each road,links between the nodes which connect respective node points, the heightof each node point (altitude), and the like.

The facility data may include, data representing hotels, gas stations,parking lots, and/or sightseeing facilities. In the navigation database64, audio output data for outputting predetermined information throughan audio output section (not shown) of the navigation unit 14 may berecorded.

The information center 62 is capable of receiving, for example, trafficinformation including congestion information, restriction information,parking lot information, traffic accident information, crowded servicearea information, and the like, which may be transmitted from trafficinformation transmission center as a traffic information provider ininformation providers, for example, VICS® (Vehicle Information andCommunication System) (not shown) center. The information center 62 isalso capable of receiving general information such as news and/orweather. The information center 62 is capable of sending the trafficinformation and general information to the personal computer 61 throughthe network 43 and recording the traffic information and generalinformation in the navigation database 64. For that purpose, astatistical data file (not shown) is formed in the navigation database64, wherein old traffic information and general information are recordedin time series and the old traffic information and general informationare subjected to a specific processing as original data to record theprocessed traffic information and general information. Note that, whenthe traffic information and general information are processed, thegeneral information is referred to if necessary.

The information center 62 may be capable of sending, not only thetraffic information and general information but also video informationof TV program, music information, music, and the like to the personalcomputer 61 through the network 43.

The information center 62 may be maintained by an individual, acorporation, an organization, a local government, a nationalgovernmental agency, or the like. The information center 62 may createthe navigation data for itself or purchase the data from otherinformation creators for distribution.

The network 43 may include a LAN (Local Area Network), a WAN (Wide AreaNetwork), an intranet, a portable phone system network, a telephone linenetwork, a public communication line network, a private communicationnetwork, the internet and/or the like. Further, the network 43 mayutilize CS broadcasting and BS broadcasting based on a broadcastingsatellite, ground wave digital TV broadcasting, FM multiplexedbroadcasting, and/or the like. The network 43 may also use communicationmeans such as non-stop electronic toll collection system (ETC) used inintelligent transport system (ITS), dedicated short-range communication(DSRC), and/or the like. Note that the personal computer 61, the server63, the provider's server, and/or the navigation processing section 17may function independently or may be combined as a multi-functioncomputer.

Next, an example of a navigation device 14 having the above-describedstructure will be described with reference to FIG. 2. FIG. 2 is adiagram for explaining the navigation device according to the firstexemplary embodiment of the invention. As shown in FIG. 2, thenavigation device 14 can include a current position detection processingsection 15 for detecting a current position, the data recording section16 in which various kinds of data may be recorded, the navigationprocessing section 17 for executing various kinds of arithmeticoperation processing based on inputted information, an input section 34as a first operating section, a display section 35 as a first notifyingsection, a voice input section 36 as a second operating section, a voiceoutput section 37 as a second notifying section, and the communicationsection 38. A vehicle speed sensor 41 is connected to the navigationprocessing section 17.

The current position detection processing section 15 can include a GPS21, a geomagnetic sensor 22, a distance sensor 23, a steering sensor 24,a gyro sensor 26, an altimeter (not shown), and/or the like.

The GPS 21 detects a current position on the earth by receiving anelectronic wave generated by an artificial satellite, the geomagneticsensor 22 detects the direction of an the user vehicle by measuringgeomagnetism, and the distance sensor 23 detects a distance betweenpredetermined positions on the road. Regarding the distance sensor 23,it is permissible to use a type which measures a revolution velocity ofwheels (not shown) and detects a distance based on the revolutionvelocity, a type which measures an acceleration and detects a distanceby integrating the acceleration twice, and/or the like.

The steering sensor 24 detects a steering angle, and may include, forexample, an optical revolution sensor attached to a revolution sectionof a steering wheel (not shown), a revolution resistance sensor, anangle sensor attached to wheels and/or the like.

The gyro sensor 26 detects a turning angle and may include, for example,a gas rate gyro, a vibration gyro and/or the like. By integrating theturning angles detected by the gyro sensor 26, the direction of the uservehicle can be detected.

Note that the GPS 21 is capable of detecting a current position byitself. However, the current position can also be detected by combininga distance detected by the distance sensor 23 with the directiondetected by the geomagnetic sensor 22, a turning angle detected by thegyro sensor 26, or a steering angle detected by the steering sensor 24.

The navigation processing section 17 can include internal storage unitssuch as a CPU 31 which works as an arithmetic operation unit and controlunit for controlling the navigation device 14, a RAM 32, which is usedas a working memory when the CPU 31 executes various kinds of arithmeticoperations, a ROM 33 which stores various kinds of programs for routesearching, route guidance, determination of specific intervals, and/orfor control. The navigation processing section 17 can include a flashmemory 30 for recording navigation data transmitted from the personalcomputer 61. The input section 34, the display section 35, the audioinput section 36, the audio output section 37 and the communicationsection 38 also may be connected to the navigation processing section17. Note that a semiconductor memory, a magnetic core, and/or the likemay be used for the RAM 32, the ROM 33, and/or the flash memory 30.Then, it is permissible to use the MPU and the like instead of the CPU31 as the arithmetic operation unit and control unit.

The data recording section 16 can include a hard disk (not shown) as arecording medium, and can include a recording head (not shown) as adriver to read out a predetermined program, data, and the like recordedin the hard disk and write predetermined data into the hard disk.

Although, according to this embodiment, the hard disk may be used as anexternal storage unit, a magnetic disk, such as a flexible disk, can beused as an external storage unit instead of the hard disk. Further, amemory card, a magnetic tape, a magnetic drum, a CD, a MD, a DVD, anoptical disk, a MO, an IC card, an optical card, and/or the like may beused as an external storage unit.

Although, according to this exemplary embodiment, the ROM 33 may storevarious kinds of programs and the data recording section 16 recordsvarious kinds of data, programs, data and/or the like can be recorded inthe same external storage unit. In this case, for example, the programs,data and/or the like can be read out from the external storage unit andwritten into the flash memory 30. Therefore, the programs, data, and/orthe like can be updated by replacing the external storage unit. If anautomatic transmission control unit for controlling an automatictransmission (not shown) loaded on a vehicle is installed, programs,data, and/or the like for controlling the automatic transmission controlunit can be also recorded in the external storage unit.

The input section 34 may be used for correcting a current position whena vehicle starts, inputting a departure point as a guidance startingpoint and a target destination as a guidance end point, and/or operatingthe communication section 38. The input section may include controlswitches (not shown) such as various kinds of keys, switches, buttonsand the like. Further, the input section 34 may include a keyboard, amouse, a bar code reader, a remote control unit for remote controloperation, a joy stick, a light-pen, a stylus pen and/or the like. Theinput section 34 may be formed by operation switches such as variouskinds of keys, switches, buttons and the like shown as images on a touchscreen forming part of the display section 35. In this case, the inputis carried out by touching the operation switches.

Various information including, for example, operation guidance,operation menus, key guidance, search results, guidance informationalong the search route, media programming, and the like may be shown onvarious kinds of screens formed on the display. The display section 35can include displays such as, for example, a CRT display, a liquidcrystal display, a plasma display and/or a hologram unit for projectinga hologram on a vehicle windshield.

The audio input section 36 may include a microphone or the like (notshown) and is capable of inputting necessary information with sound. Theaudio output section 37 can include a voice synthesizer and a speaker(not shown). The search route, guidance information, and/or the like maythen be outputted with voice synthesized by the voice synthesizer fromthe audio output section 37. Note that, it is possible to output notonly voice synthesized by the voice synthesizer, but also various otherkinds of sounds and variety of guidance information recorded in advancein a tape, memory or the like.

The communication section 38 can include a beacon receiver that receivestraffic information including congestion information, restrictioninformation, parking lot information, traffic accident information,and/or service area information, transmitted from a traffic informationtransmission center, for example, the VICS® center, in the form ofelectric wave beacon signals, light beacon signals or the like viaelectric wave beacon units, light beacon units, or the like disposedalong a road. The communication section 38 can also include an FMreceiver for receiving FM multiplexed information constituted of generalinformation such as news, weather forecast in the form of FM multiplexedbroadcasting via an FM broadcasting station.

The communication section 38 is capable of receiving various kinds ofdata such as D-GPS information for detecting a detection error in theGPS 21. The communication section 38 is also capable of receivingposition information based on the electric wave beacon signals, lightbeacon signals, and the like to detect the current position, and thusmay function as a current position detecting section.

The navigation device 14 and the personal computer 61 (FIG. 1) may beconnected to each other by wireless LAN which enables bi-directionalcommunication. Accordingly, the communication section 75 may be providedwith access points as described above while slots (not shown), such asPCMCIA slot, PC card slot may be formed in the communication section 38,so that a radio card (not shown) can be inserted into the slot. Althoughaccording to this exemplary embodiment, the navigation device 14 and thepersonal computer 61 may be connected to each other by the wireless LAN,according to various other exemplary embodiments, the navigation device14 and the personal computer 61 may be connected by wired LAN. Accordingto those exemplary embodiments, the communication section 75 can beprovided with hubs, so that the hubs and the communication section 38are detachably coupled by a cable.

Next, the operation of a navigation system having the above-describedstructure will be described with reference to FIGS. 3-7. FIG. 3 is amain flow chart indicating the operation of a personal computeraccording to the first exemplary embodiment of the invention. FIG. 4 isa diagram showing the sub-routine of compression processing according tothe first exemplary embodiment of the invention. FIG. 5 is a flow chartshowing the operation of the navigation device according to the firstexemplary embodiment of the invention. FIG. 6 is a diagram showing thedata structure of the compressed data according to the first exemplaryembodiment of the invention. FIG. 7 is a diagram showing the datastructure upon decompression processing according to the first exemplaryembodiment of the invention.

As shown in FIG. 3, if an operator inputs a departure point and a targetdestination by operating the operation section 73 of the personalcomputer 61 (FIG. 1), the CPU 71 executes search condition settingprocessing, in which the departure point and target destination are setas the search conditions, and the search conditions are transmitted tothe information center 62 (step S1).

If as the user terminal, for example, a PDA or the like is used insteadof the personal computer 61, a GPS card can be set in, for example, aPCMCIA slot in the PDA, a PC card slot, and a current position detectedby the GPS card can be set as the departure point.

If the search conditions are received by the server 63 in theinformation center 62, the server 63 executes information obtainmentprocessing, reads out the search data in the navigation database 64,reads out statistical data and reads traffic information transmitted bythe VICS (registered trade mark) so as to obtain information necessaryfor searching a route.

Subsequently, the server 63 executes search processing, in which a routeis searched based on search data, traffic information, statistical dataand the like according to the search conditions.

If a route is searched for by the server 63, the server 63 transmitsroute data indicating, for example, a search route, map data indicatinga map of a surrounding area of the search route, audio output data forguiding along the search route through the audio output section 37 (FIG.2), and the like to the personal computer 61 as the route guidance data.

The route data may contain road data (road attribute and the like) whichconstitutes the search route, and the map data may contain areainformation such as areas containing the search route and areas adjacentto the areas containing the search route.

Each area consists of map data of a square region of predetermined size.Each area may be set such that, for example, the quantity of the mapdata, is within a specified range, and each area is supplied with aparcel number as an identification number. The surface area of each areadiffers between an area having a large amount of information containedin the map data like urban area and an area having a small amount of mapdata like suburban area. For example, if an area is composed of 128 Kbyte of data that area may correspond to a 4-Km square region on themap. Comparatively, an area having a larger amount of informationcontained in the map data may correspond to a 2-Km square region on themap, and an area having a smaller amount of information contained in themap data may correspond to an 8-Km square region.

Although according to this exemplary embodiment, the server 63 searchesfor a route based on search data, traffic information, statistical dataand the like, according to various other exemplary embodiments, theserver 63 may search for a route based on only the search data. In thiscase, the server transmits route data indicating a search route to thepersonal computer 61 as route guidance data.

Although according to this exemplary embodiment, the audio output datamay be transmitted from the information center 62 to the personalcomputer 61, according to various other exemplary embodiments, the audiooutput data may be recorded in the data recording section 16 of thenavigation device 14 in advance. In this case, the voice output datadoes not need to be transmitted as part of the route guidance data.

In the personal computer 61, if the route guidance data is transmitted,the CPU 71 carries out reception processing to receive the routeguidance data, and subsequently, the CPU 71 executes recordingprocessing to download the route guidance data into a hard disk in therecording unit 74 for recording (step S2).

When a vehicle is parked in a garage, for example, the operator cantransfer the route guidance data, which is downloaded into the harddisk, to the navigation device 14 by operating the operation section 73and record it in the flash memory 30, for example, in the navigationprocessing section 17.

If the communication time required for transmitting the route guidancedata to the navigation device 14 is long, the power supply (not shown)in the navigation device 14 needs to be providing power during thistime. Therefore, the amount of electric power consumed by the navigationdevice 14 increases and a load applied to a battery (not shown) mountedon the vehicle increases tremendously.

If the required communication time is long, the operator needs tomonitor the personal computer 61 during this time. Thus, not onlymonitoring the personal computer 61 is troublesome, but also a cost forthe lengthy transmission is increased.

Thus, according to this exemplary embodiment, the CPU 71 may executecompression processing to compress the route guidance data downloadedinto the hard disk to produce compressed data, and the compressed datais transferred to the navigation device 14 (step S3).

In this case, the navigation device 14 needs to decompress thecompressed data in order to access the route guidance data. Because theroute guidance data cannot be used until all the compressed data isdecompressed, the vehicle cannot be started immediately along a searchroute.

The CPU 71 reads out the route guidance data from the hard disk andafter the navigation device 14 starts up, the route guidance data isdivided into, for example, surrounding data and other non-surroundingdata depending on whether a user needs it immediately (surrounding data)or not (non-surrounding data), (step S3-1). Note that the surroundingdata refers to the route guidance data in an area or areas near adeparture point (a current position in case where the search route isfrom the current position to a target destination). The non-surroundingdata refers to the route guidance data in areas that do not contain thedeparture point. It is also possible to include the route guidance dataof one or more areas adjacent to the area containing the departure pointin the surrounding data, if necessary.

Then the compression processing means compresses the route guidance dataon the surrounding data and non-surrounding data (step S3-4) to createcompressed data supplied with an administration header (step S3-3), andthe compressed data is recorded in the flash memory of the recordingunit 74. Note that the administration header is information forcontrolling the compressed data and as shown in FIG. 6, constituted ofan administration ID identifying the compressed data, data sizeindicating the size of the compressed data, other data, and the like.

Thus, the compression processing means determines whether a dividedroute guidance data is surrounding data (step S3-2). If the dividedroute guidance data is the surrounding data, the administration headeris supplied with information regarding the surrounding data accompaniedby the compression (step S3-3) and according to this exemplaryembodiment, such information can include information about the positionincluding a starting point of the route guidance data. Although,according to this exemplary embodiment, the position information can bein the form of, for example, coordinates, it may also be represented byroad number, node number, or the like.

If the compressed data is recorded, the CPU 71 executes compressed datatransmission processing to transfer the compressed data to thenavigation device 14. Thus, if the operator operates the operationsection 73 to give instruction for activating the navigation device 14,CPU 71 executes navigation device start processing to turn on the powerof the navigation device 14 to start the navigation device 14 (step S4).Subsequently, the CPU 71 executes data transfer processing to read outcompressed data from the flash memory of the recording unit 74 andtransfer to the navigation device 14 (step S5). In the navigation device14, the CPU 31 executes compressed data recording processing to recordthe compressed data into the flash memory 30.

If all the compressed data is recorded in the flash memory 30, the CPU71 executes navigation device stop processing to stop the navigationdevice 14 (step S6), so that the compressed data is stored in thenavigation device 14 and available.

As described above, when the route guidance data is transferred from thepersonal computer 61 to the navigation device 14, the route guidancedata is compressed. Thus, the data size of that compressed data can bereduced. Therefore, required communication time is shortened and thetime in which the navigation device 14 is powered on can be reduced.Thus, power consumed by the navigation device 14 is decreased, and theload applied to a battery mounted on a vehicle can be reduced.

Further, because the communication required time is short, the operatordoes not need to monitor the personal computer 61 for as long, therebyworkload is reduced as well.

Next, the operation of the navigation device 14 when a vehicle is drivenwill be described with reference to FIG. 5. First, when the ignitionswitch of a vehicle is turned on, the navigation device 14 starts (stepS11). Then, a current position is detected by the GPS 21 and thedirection of the vehicle is detected based on, for example, a turningangle of the vehicle detected by the gyro sensor 26.

Next, the CPU 31 executes decompression processing to decompress thecompressed surrounding data giving priority based on the currentposition (step S12). Thus, the CPU 31 reads the current position andreads out compressed data from the flash memory 30 to read the positioninformation within the administration header of the compressed data.Subsequently, the CPU 31 determines whether the compressed data issurrounding data by comparing a current position of the vehicle with theposition information in the administration header. If the compresseddata is surrounding data, the CPU 31 decompresses the compressed datafor the surrounding data as shown in FIG. 7 to create decompressed dataand then, records the decompressing route guidance data into a hard diskin the data recording section 16. Note that the decompressed routeguidance data may be recorded in the flash memory 30 instead of the harddisk.

If the CPU 31 fails in the decompression processing, it can execute thedecompression processing again by re-reading out the compressed datafrom the flash memory 30.

The CPU 31 executes route guidance processing to read out route guidancedata from the hard disk in the data recording section 16, forms a mapscreen on a display of the display section 35 based on the routeguidance data, indicates a current position, surrounding map anddirection of the vehicle on the map screen, displays a search route in asurrounding area of the current position, and/or notifies a driver ofthe search route through a message from the voice output section withaudio in order to execute route guidance (step S13). Accordingly, adriver can drive a vehicle following the current position, surroundingmap, direction of the vehicle and search route displayed on the mapscreen.

If decompression of compressed data for the surrounding data iscompleted and the route guidance data is recorded in the hard disk inthis way, the CPU 31 then reads out the remaining non-surroundingcompressed data from the flash memory 30, decompresses the remainingcompressed data on the non-surrounding areas and records thedecompressed route guidance data into the hard disk in the datarecording section 16. Note that, it may alternatively be recorded inanother region of the flash memory 30 instead of the hard disk.

Regarding the surrounding data, the decompression processing is carriedout immediately after the ignition switch is turned on and thenavigation device 14 starts. Thus, the vehicle can be driven immediatelyusing the route guidance data for the area surrounding the vehicle.

Although according to this exemplary embodiment, the decompressionprocessing is carried out after the ignition switch is turned on,according to various other exemplary embodiments, the decompressionprocessing may be carried out at a predetermined timing after theignition switch is turned on, for example, after the vehicle has startedmoving.

According to various other exemplary embodiments, after the CPU 31records compressed data into the flash memory 30, the route followingmay be carried out before the CPU 71 stops the navigation device 14, inorder to decompress the compressed data and record the route guidancedata. First, if a current position is detected by the GPS 21, the CPU 31reads the current position and reads out compressed data from the flashmemory 30. The CPU 31 then reads position information in theadministration header of the compressed data. The CPU 31 determineswhether the compressed data is surrounding data by comparing the currentposition of the vehicle with the position information in theadministration header. If the compressed data is surrounding data, thecompressed data of the surrounding data is decompressed. The thusdecompressed route guidance data is recorded in the hard disk of thedata recording section 16. Note that it also can be recorded in theflash memory 30 instead of the hard disk.

After the ignition switch is turned on, the CPU 31 reads out theremaining non-surrounding compressed data form the flash memory 30,decompresses the compressed data of the non-surrounding data, and then,records the non-surrounding route guidance data into the hard disk ofthe data recording section 16. Note that it also can be recorded in theflash memory 30 instead of the hard disk.

Next, a second exemplary embodiment of the invention in whichcompression processing is executed by the information center 62 will bedescribed with reference to FIG. 8. FIG. 8 is a main flow chart showingthe operation of a personal computer according to the second exemplaryembodiment of the invention.

First, if the operator inputs a departure point and a target destinationby operating the operating section 73 of the personal computer 61(FIG. 1) as a user terminal, the CPU 71 executes search condition setprocessing, in which the departure point and the target destination areset as a search conditions (step S21) and then, the search conditionsare transmitted to the information center 62 which is an informationprovider.

When the search conditions are received by the server 63, the server 63executes information obtainment processing to obtain informationnecessary for searching for a route by reading the search data in thenavigation database 64, reading statistical data and reading trafficinformation transmitted from the VICS (registered trade mark) center.Then, the server 63 executes search processing to search for a routebased on search data, traffic information, statistical data and the likeaccording to the search condition.

If a route is searched for by the server 63, the server 63 executescompression processing, in which route guidance data, such as route dataindicating a search route, map data indicating a map of a surroundingregion of the search route, audio output data for guiding along thesearch route through the audio output section 37 and/or the like, iscompressed to create compressed data and the compressed data is recordedin a recording unit (not shown) in the server 63.

The server 63 divides the route guidance data into surrounding data andnon-surrounding data. Then, the surrounding data is provided with anadministration header including position information. Subsequently, theserver 63 executes compression data transmission processing to transmitthe compressed data to the personal computer 61.

When the compressed data is transmitted, the CPU 71 executes recordingprocessing to download the compressed data into the hard disk of therecording unit 74 (step S22). As described above, the CPU 71 thentransmits the compressed data to the navigation device 14 (step S24).Since the operation of the navigation device 14 after compressed data istransferred is the same as that of the first embodiment, descriptionthereof is omitted.

Since according to this exemplary embodiment, the surrounding data isdecompressed immediately after the ignition switch is turned on and thenavigation device 14 starts up (step S23), the vehicle can be startedimmediately utilizing the route guidance data.

Although according to this exemplary embodiment, the decompressionprocessing is executed after the ignition switch is turned on, accordingto various other exemplary embodiments, the decompression processing maybe executed at a predetermined timing after the ignition switch isturned on, for example, after the vehicle has started moving.

According to various other exemplary embodiments, route following may becarried out after the CPU 71 records compressed data in the flash memory30 and before the CPU 71 stops the navigation device 14, anddecompression of the compressed data and recording of the route guidancedata are carried out. First, when a current position is detected by theGPS 21, the CPU 31 reads the current position, reads out the compresseddata from the flash memory 30, and then reads the position informationwithin the administration header of the compressed data. Subsequently,the CPU 31 determines whether the compressed data is surrounding data bycomparing the current position with the position information in theadministration header. If the compressed data is surrounding data, theCPU 31 decompresses the compressed data of the surrounding data, andthen records the route guidance data into the hard disk of the datarecording section 16. Note that it is also possible to record the datain the flash memory 30 instead of the hard disk.

If decompression of the compressed surrounding data is completed and thedecompressed route guidance data is recorded in the hard disk, the CPU31 reads out the remaining non-surrounding compressed data from theflash memory 30, decompresses the compressed data of the non-surroundingdata and records the non-surrounding route guidance data into the harddisk of the data recording section 16. Note that it is also possible torecord the data in the flash memory 30 instead of the hard disk.

According to the first and second exemplary embodiments, the routeguidance data is divided into surrounding data and non-surrounding data,and the surrounding data is compressed with an administration headerincluding position information, while the non-surrounding data iscompressed as is (i.e., without an administration header). A thirdexemplary embodiment in which the surrounding data may not be compressedwill be described with reference to FIGS. 9-12.

In this case, if the amount of the surrounding data is large and thus apredetermined compression condition is established, the surrounding datais compressed. If the amount of the surrounding data is small and thusthe compression condition is not established, the surrounding data isnot compressed. For example, a required communication time when thesurrounding data is transferred from the personal computer 61 to thenavigation device 14 without being compressed is assumed to be τ 1, therequired communication time for the compressed surrounding data isassumed to be τ 2, and a time necessary for decompressing the compressedsurrounding data (hereinafter referred to as “decompression time”) isassumed to be τ 3. According to the third exemplary embodiment, if therequired communication times τ 1, τ 2 and the decompression time τ 3have the relation of τ 1>τ 2+τ 3, the compression condition isestablished, and if there is a relation of τ 1≦τ 2+τ 3, the compressioncondition is not established.

FIG. 9 is a main flow chart showing the operation of the personalcomputer according to the third exemplary embodiment of the invention.FIG. 10 is a diagram showing the sub-routine of a partial compressionprocessing according to the third exemplary embodiment of the invention.FIG. 11 is a main flow chart showing the operation of the navigationdevice according to the third exemplary embodiment of the invention.FIG. 12 is a diagram showing the sub-routine of decompression processingaccording to the third exemplary embodiment of the invention.

First, if the operator inputs a departure point and a target destinationby operating the operating section 73 of the personal computer 61 (FIG.1), the CPU 71 executes search condition set processing, in which thedeparture point and target destination are set as search conditions(step S31) and then, the search condition is transmitted to theinformation center 62.

When the search condition is received by the server 63, the server 63executes information obtainment processing to obtain informationnecessary for searching for a route by reading the search data in thenavigation database 64, reading statistical data in the navigationdatabase 64, and reading traffic information transmitted from the VICS(registered trade mark) center.

Then, the server 63 executes search processing to search for a routebased on the search data, the traffic information, the statistical data,and the like, according to the search conditions. When a route issearched for by the search processing means, the server 63 executesroute search data transmission processing, in which route dataindicating a search route, map data indicating a surrounding map of thesearch route, audio output data for guiding along the search route bythe voice output section 37 (FIG. 2) and the like are transmitted to thepersonal computer 61 as route guidance data.

When the route guidance data is transmitted, the CPU 71 executesrecording processing, in which the route guidance data is downloadedinto the hard disk of the recording unit 74 (step S32). Next, the CPU 71executes a partial compression processing (step S33) to read out theroute guidance data from the hard disk and divide the route guidancedata into surrounding data and non-surrounding data (step S34). The CPU71 records the non-compressed surrounding data into the flash memory.The non-surrounding route guidance data is compressed with anadministration header (step S33-3). Thus, partially compressed data iscreated and then recorded in the flash memory of the recording unit 74.

If the partially compressed data is created in this way, the CPU 71transmits the partially compressed data to the navigation device 14. Ifthe operator instructs a start of the navigation device 14 by operatingthe operating section 73, the CPU 71 executes navigation device start-upprocessing, to turn on the navigation device 14 to start the navigationdevice 14 (step S34). Subsequently, the CPU 71 executes datatransferring processing to read out the partially compressed data fromthe flash memory of the recording unit 74 and transmit it to thenavigation device 14 (step S35). The CPU 31 in the navigation device 14executes partially compressed data recording processing to record thepartially compressed data into the flash memory 30.

If all the partially compressed data is recorded in the flash memory 30,the CPU 71 executes navigation device stop processing to stop thenavigation device 14 (step S36) so that the partially compressed data isstored in the navigation device 14 and available.

Next, the operation of the navigation device 14 when a vehicle is drivenwill be described. When the ignition switch of a vehicle is turned on,the navigation device 14 starts up (step S41), so that a currentposition is detected by the GPS 21, and the direction of the vehicle isdetected based on, for example, the turning angle of the vehicledetected by the gyro sensor 26.

Then, the CPU 31 executes route guidance processing to read out thepartially compressed data from the flash memory 30. For the surroundingdata, the CPU 31 forms a map screen on the display of the displaysection 35 based on the non-compressed route guidance data in thepartially compressed data. The CPU 31 displays a current position, asurrounding map, the direction of the vehicle, and a search route in thesurrounding area of the current position (step S42). The CPU 31 can alsonotify a driver of the search route with a message from the audio outputsection.

If the route guidance starts up in this way, the CPU 31 can executedecompression processing (step S43) and decompresses the non-surroundingdata (step S43-2) of the partially compressed data and record the routeguidance data into the hard disk of the data recording section 16. Notethat the data may be recorded in the flash memory 30 instead of the harddisk.

As for the surrounding data, if the ignition switch is turned on toactivate the navigation device 14, the route guidance data is readwithout being decompressed, so that a vehicle can be run immediatelyusing the route guidance data.

Next, the fourth exemplary embodiment of the invention, in which thecompression processing is executed by compressing the non-surroundingdata without compressing the surrounding data by the information center62, will be described with reference to FIG. 13. FIG. 13 is a main flowchart showing the operation of the personal computer according to thefourth exemplary embodiment of the invention. First, if the operatorinputs a departure point and a target destination by operating theoperating section 73 of the personal computer 61 (FIG. 1). The CPU 71executes search condition set processing, in which the departure pointand target destination are set as search conditions (step S51) and then,the search conditions are transmitted to the information center 62.

When the search condition is received by the server 63, the server 63executes information obtainment processing to obtain informationnecessary for searching for a route by reading the search data in thenavigation database 64, reading statistical data in the navigationdatabase 64, and reading traffic information transmitted from the VICS(registered trade mark) center.

Subsequently, the server 63 executes search processing to search for aroute based on the search data, the traffic information, the statisticaldata and the like according to the search conditions.

If a route is searched for by the server 63, the server 63 executes apartial compression processing, in which route guidance data, such asdata indicating a search route, data indicating a map of a surroundingregion of the search route, audio output data for guiding along thesearch route using the audio output section 37 (FIG. 2) and the like, asthe route guidance data is compressed to create partially compresseddata, and the partially compressed data is recorded in a recording unitin the server 63.

In this case, the server 63 divides the route guidance data intosurrounding data and non-surrounding data. The partially compressed dataincludes non-compressed surrounding data and compressed non-surroundingdata. Subsequently, the server 63 executes partially compressed datatransmission processing to transmit partially compressed data to thepersonal computer 61.

Then, when the partially compressed data is transmitted, the CPU 71executes recording processing to download the partially compressed datainto the hard disk of the recording unit 74 (step S52). Next, the CPU 71transfers the partially compressed data to the navigation unit 14 asdescribed above. Note that, since the operation of the navigation device14 after the partially compressed data is transferred is the same asthat of the third embodiment, description thereof is omitted.

According to the second and fourth exemplary embodiments, compresseddata and partially compressed data and the like may be transmitted fromthe information center 62 and downloaded into the hard disk of thepersonal computer 61 and the compressed data, partially compressed dataand the like are transferred to the navigation device 14. According tothe fifth exemplary embodiment in which the compressed data transmittedfrom the information center 62 is received directly by the navigationdevice 14 will be described with reference to FIG. 14. According to thefifth exemplary embodiment, the navigation device 14 and the informationcenter 62 can be connected to each other via the network 43 constitutedof, for example, portable phone network so as to enable bi-directionalcommunication. For that purpose, the communication section 38 may be aportable phone and can communicate with the server 63 of the informationcenter 62 via a base station (not shown). FIG. 14 is a main flow chartshowing the operation of a navigation device according to the fifthexemplary embodiment of the invention.

If the ignition switch of a vehicle is turned on, the navigation device14, which is an on-board device (FIG. 2), starts so that a currentposition is detected by the GPS 21 and the direction of the vehicle isdetected based on the turning angle of the vehicle detected by the gyrosensor 26.

If the operator inputs a departure point and a target destination byoperating the input section 34 in the navigation device 14, the CPU 31executes search condition set processing, in which a departure point anda target destination are set up as search conditions (step S61), andthen transmits the search condition to the information center 62 whichis an information provider.

Next, when the search conditions are received by the server 63 (FIG. 1),the server 63 executes information obtainment processing to read out thesearch data in the navigation database 64, and then reads outstatistical data and reads traffic information transmitted from the VICS(registered trade mark) center to obtain information necessary forsearching for a route. The server 63 searches for a route based onsearch data, traffic information, statistical data and the likeaccording to the search conditions.

If a route is searched for by the server 63, the server 63 executescompression processing and compresses route data indicating a searchroute, map data indicating a map of a surrounding region of the searchroute, audio output data for guiding along the search route by the audiooutput section 37 and the like as the route guidance data and recordsthe compressed data in the recording unit of the server 63.

In this case, the server 63 divides the route guidance data intosurrounding data and non-surrounding data and creates compressed datasupplied with an administration header. The surrounding data in theroute guidance data includes position information. Subsequently, theserver 63 executes compressed data transmission processing to transmitthe compressed data to the navigation device 14.

When the compressed data is transmitted, the CPU 31 in the navigationdevice 14 executes reception processing to receive compressed data. Thecompressed data recording processing means of the CPU 31 executescompressed data recording processing, in which the compressed data isdownloaded into the flash memory 30 and recorded (step S62).

Subsequently, the CPU 31 executes decompression processing to decompresscompressed data (step S63). Thus, the CPU 31 reads a current position,reads out compressed data from the flash memory 30, and then readsposition information in the administration header of the compresseddata. The CPU 31 determines whether the compressed data is surroundingdata by comparing the current position with position information fromthe administration header. If the compressed data is surrounding data,it decompresses the compressed data and records the decompressed routeguidance data into the hard disk of the data recording section 16. Notethat the data may be recorded in the flash memory 30 instead of the harddisk.

The CPU 31 executes route guidance processing to read out the routeguidance data from the hard disk of the data recording section 16 andforms a map screen on a display of the display section 35 based on theroute guidance data. The CPU 31 can also display a current position, amap of a surrounding region, the direction of the vehicle on the mapscreen, and a search route in the surrounding region of the currentposition. The CPU 31 can notify a driver of the search route with voicethrough a message from the voice output section in order to executeroute guidance (step S64). Thus, the driver can drive a vehicleaccording to the current position, a map of a surrounding region,direction of the vehicle, and search route displayed on the map screen.

If decompression of the compressed data on the surrounding data iscompleted (step S65) and the route guidance data is recorded in the harddisk, the CPU 31 reads out the remaining compressed data from the flashmemory 30 and decompresses the compressed data on the non-surroundingdata and then records the non-surrounding route guidance data into thehard disk of the data recording section 16. Note that the data may berecorded in the flash memory 30 instead of the hard disk.

Next, a sixth exemplary embodiment in which partially compressed datatransmitted from the information center 62 is directly received by thenavigation device 14 will be described with reference to FIG. 15. FIG.15 is a main flow chart showing the operation of the navigation deviceaccording to the sixth exemplary embodiment of the invention.

If the ignition switch of a vehicle is turned on, the navigation device14 starts so that a current position is detected by the GPS 21 and thedirection of the vehicle is detected based on the turning angle of thevehicle detected by the gyro sensor 26.

If the operator inputs a departure point and a target destination byoperating the input section 34 in the navigation device 14, the CPU 31executes search condition set processing, in which a departure point anda target destination are set (step S71) and then, transmits the searchconditions to the information center 62 (FIG. 1).

When the search condition is received by the server 63, the server 63executes information obtainment processing to read out the search datain the navigation database 64 and then reads out statistical data andreads traffic information transmitted from the VICS (registered trademark) center to obtain information necessary for searching for a route.The server 63 searches for a route based on search data, trafficinformation, statistical data, and the like according to the searchconditions.

When a route is searched for by the server 63, the server 63 executespartial compression processing and partially compresses the routeguidance data, such as route data, map data of a surrounding region ofthe search route, audio output data and the like, as the route guidancedata and records the partially compressed data in the recording unit ofthe server 63.

The server 63, in order to create the partially compressed data, dividesthe route guidance data into surrounding data and non-surrounding data(e.g., step S33-1), and only compresses the non-surrounding data (e.g.,step S33-3). Subsequently, the server 63 executes partially compresseddata transmission processing to transmit the partially compressed datato the navigation device 14.

When the partially compressed data is transmitted, the CPU 31 executespartially compressed data recording processing to download the partiallycompressed data into the flash memory 30 (step S72).

Next, the CPU 31 executes route guidance processing to read out thepartially compressed data from the flash memory 30 and forms a mapscreen on a display of the display section 35 based on thenon-compressed surrounding data of the partially compressed data, andindicates a current position, a map of a surrounding region, thedirection of the vehicle on the map screen, and then notifies the driverof a search route with a message from the audio output section forguidance of the search route (step S73).

After the route guidance starts, the CPU 31 executes partialdecompression processing, and decompresses the non-surroundingcompressed data (e.g., step S43-2) in the partially compressed data(step S74) into the hard disk of the data recording section 16 until ithas all been decompressed (step S75).

According to the first, second and fifth exemplary embodiments, the CPU31 reads out the compressed data from the flash memory 30 after avehicle starts traveling and decompresses the compressed non-surroundingdata. However, while traveling, the current position of the vehiclechanges. Therefore, it is possible to compare an updated currentposition with position information of the non-surrounding data of anarea near the updated current position, decompress that data and recordthe decompressed data in the hard disk of the data recording section 16.In this case, an administration header with position information mustalso be provided for the non-surrounding data. Additionally, it ispossible to include data within the administration header that links thedata for one area with the data for areas surrounding that area anddecompress such surrounding data successively the current position isupdated.

The non-surrounding data can also be divided into a plurality of smalldivided data portions. The surrounding data and each small dividednon-surrounding data portion can be compressed at different compressionrates. Thus, according to the seventh exemplary embodiment thenon-surrounding data is divided into route-surrounding data as a firstsmall divided data portion and non-route-surrounding data as a secondsmall divided data portion. Note that, since the method steps until theroute guidance data transmitted from the information center 62 to thepersonal computer 61 is recorded in the hard disk of the recording unit74 is the same as that of the first exemplary embodiment, descriptionthereof will be omitted.

FIG. 16 is a diagram showing the sub-routine of compression processingaccording to the seventh exemplary embodiment of the invention. FIG. 17is a flow chart showing the operation of the navigation device accordingto the seventh exemplary embodiment of the invention. FIG. 18 is adiagram showing the data structure of compressed data according to theseventh exemplary embodiment of the invention. FIG. 19 is a diagramshowing the data structure upon decompression processing of surroundingdata according to the seventh exemplary embodiment of the invention.

According to the seventh exemplary embodiment, the CPU 71 in thepersonal computer 61 (FIG. 1), executes compression processing to readout the route guidance data from the hard disk and divide the routeguidance data into surrounding data, route-surrounding data and othernon-route-surrounding data (step S3-11). The route-surrounding data is,for example, route guidance data in an area or areas adjacent to areassurrounding the search route.

The CPU 71 compresses the route guidance data on the surrounding data,route-surrounding data and non-route-surrounding data to createcompressed data supplied with an administration header and records eachcompressed data into the flash memory of the recording unit 74. In thiscase, different compression rates α1-α3 of the surrounding data,route-surrounding data and non-route-surrounding data are set up. Sincethe surrounding data needs to be decompressed immediately after theignition switch in the navigation device 14 is turned on, thecompression rate al is set low. Since the route-surrounding data isdecompressed after the vehicle has started traveling, the compressionrate α2 is set to a medium level. And since the non-route-surroundingdata is decompressed after the traveling of a vehicle is started, forexample, when a vehicle goes off a search route so that an off route(leaving the route) occurs, the compression rate α3 is set to a highlevel. Consequently, the compression rates α1-α3 are set into therelation of α3<α2<α1. The compression rates α1-α3 may be expressed inpercentage to the data amount before a compression, and the higher thecompression rate α1-α3, the smaller the percentage value, while thelower the compression rate α1-α3, the larger the percentage value.

The CPU 71 compresses the route guidance data about the surrounding dataat the compression rate α1 (step S3-14), about the route-surroundingdata at the compression rate α2 (step S3-16), and about thenon-route-surrounding data at the compression rate α3 (step S3-17) tocreate compressed data supplied with an administration header (stepS3-13) and record the each compressed data into the flash memory of therecording unit 74. Note that the administration header is informationfor controlling compressed data and as shown in FIG. 18, includes anadministration ID identifying the compressed data, data size indicatingthe size of the compressed data and other data. The data size of thesurrounding data with respect to the data amount of compressed datathereof is large, the data size of the route-surrounding data withrespect to the data amount of the compressed data thereof is medium, andthe data size of the non-route-surrounding data with respect to the dataamount of the compressed data thereof is small.

The CPU 71 determines whether the divided route guidance data issurrounding data (step S3-12). Then, if the divided route guidance datais surrounding data, an administration header is supplied with positioninformation or the like accompanied by compression (step S3-13).Although according to this embodiment, the position information isexpressed with, for example, coordinate, it may be expressed with a roadnumber, node number or the like.

If the compressed data is created in this way, the CPU 71 executescompressed data transmission processing to transfer the compressed datato the navigation device 14. Thus, if an operator starts the navigationdevice 14 by operating the operating section 73, the CPU 71 executesnavigation device start processing to turn on the navigation device 14.Subsequently, the CPU 71 executes data transmission processing to readout compressed data from the flash memory of the recording device 74 andtransfer the compressed data to the navigation device 14. The CPU 31(FIG. 2) in the navigation device 14 executes compressed data recordingprocessing to record compressed data into the flash memory 30.

When all of the compressed data is recorded in the flash memory 30, theCPU 71 executes navigation device stop processing to stop the navigationdevice 14.

Because the route guidance data is transmitted from the personalcomputer 61 to the navigation device 14 in a compressed form, the datasize of the data is reduced. Furthermore, because the compression rateα2 of the route-surrounding data is higher than the compression rate α1of the surrounding data, and the compression rate α3 of thenon-route-surrounding data is higher than the compression rate α2 of theroute-surrounding data, the data size of the compressed data can bereduced to about ⅓. Thus, the required communication time becomessufficiently short and a time in which the navigation device 14 ispowered on may be reduced sufficiently, so that power consumed by thenavigation device 14 is decreased. Consequently, load applied to abattery mounted on a vehicle can be decreased.

It should be appreciated that the speed of decompressing the surroundingdata is higher than the decompressing speed of the route-surroundingdata by the same degree that the compression rate al is lower than thecompression rate α2, and the decompressing speed of theroute-surrounding data is higher than the decompression speed of thenon-route-surrounding speed by the same degree that the compression rateα2 is lower than the compression rate α3.

Next, the operation of the above-described navigation device 14 when avehicle is driven will be described. First, if the ignition switch of avehicle is turned on, the navigation device 14 starts (step S81), sothat a current position is detected by the GPS 21 and the direction ofthe vehicle is detected based on a turning angle of the vehicle detectedby the gyro sensor 26.

Next, the CPU 31, executes surrounding data decompression processing todecompress the surrounding compressed data giving priority to that datasurrounding data that is closest to a current position. Thus, the CPU 31reads a current position of the vehicle, reads out compressed data fromthe flash memory 30, and reads the position information in theadministration header of the compressed data. The CPU 31 determineswhether the compressed data is surrounding data by comparing a currentposition of the vehicle with the position information or the compressedsurrounding data. If the compressed data is surrounding data, thecompressed data on the surrounding data is decompressed giving priorityto that data closest to the current position as shown in FIG. 19 and thedecompressed route guidance data, which is the decompressed data, isrecorded in the hard disk of the data recording section 16 (step S82).Note that the data may be recorded in the flash memory 30 instead of thehard disk.

Then, the CPU 31 executes route guidance processing to determine whetherall surrounding data is decompressed (step S83), and if all of thesurrounding data is decompressed, the route guidance is started (stepS84). Accordingly, the CPU 31 reads out route guidance data from thehard disk of the data recording section 16, forms a map screen on adisplay of the display section 35 based on the route guidance data,displays a current position, a map of a surrounding region and thedirection of the vehicle on the map screen, displays a search route inthe surrounding region of the current position, and notifies a driver ofthe search route with a message from the audio output section 37 forguidance of the route.

Subsequently, the CPU 31, executes route-surrounding data decompressionprocessing, in which the compressed route surrounding data isdecompressed (step S85) and recorded in the hard disk of the datarecording section 16.

The route guidance processing means determines whether route-surroundingdata is decompressed (step S86). If all the route-surrounding data isdecompressed, the route guidance data is read out from the hard disk ofthe data recording section 16 and the map screen is formed on a displayof the display section 35 based on the route guidance data. The displaysection 35 displays a current position, a map of a surrounding regionand the direction of the vehicle on the map screen, displays a searchroute in the surrounding region of the current position, and notifies adriver of the search route with audio through a message from the audiooutput section 37 in order to execute route guidance.

When a vehicle is driven along a search route, a driver mayintentionally or by mistake drive the vehicle along a mistaken routedifferent from the search route. Thus, the CPU 31 may execute off routedetermination processing, in which it reads a current position anddetermines whether or not the vehicle is off of the route based on thecurrent position and route data (step S87). If the vehicle is off of theroute, the CPU 31 executes the non-route-surrounding data decompressionprocessing to decompress the non-route-surrounding data (step S80) andrecords the non-route-surrounding route guidance data into the hard diskof the data recording section 16.

It should be appreciated that the non-route-surrounding datadecompression may give preference to the non-route-surrounding data thatis most likely to be utilized for a re-search, solely as non-routesurrounding data in areas between the current position and the originalroute.

The CPU 31 executes re-search processing to first determine whether all(or the pertinent portion) of the non-route-surrounding data isdecompressed (step S89). If all non-route-surrounding data isdecompressed, the current position and non-route-surrounding data areread in and a route from a current position to the original search routeis re-searched for according to the non-route-surrounding data.

Although according to this exemplary embodiment, the compressionprocessing is executed by the personal computer 61, according to variousother exemplary embodiments, the compression processing may be carriedout in the information center 62. Thus, in the compression processing ofthe information center 62, the route guidance data is divided intosurrounding data and non-surrounding data, and the non-surrounding datais further divided into route-surrounding data and othernon-route-surrounding data and then, the surrounding data,route-surrounding data and non-route-surrounding data are compressed atthe respective compression rates α1-α3.

According to an eighth exemplary embodiment, if the amount of thesurrounding data is large and a predetermined compression condition isestablished, the surrounding data is compressed. However, if the amountof surrounding data is small and the compression condition is notestablished, the surrounding data is not compressed. For example, if arequired communication time when the surrounding data is transferredfrom the personal computer 61 to the navigation device 14 without beingcompressed is τ1, the required communication time for the compresseddata of the surrounding data is τ2 and a decompression time is τ3, whenthe communication required time τ1, τ2 and the decompression time τ3 arein the relation of τ1>τ2+τ3, a compression condition is established, andif there is a relation of τ1≦τ2+τ3, the compression condition is notestablished. Because the method until the route guidance datatransmitted from the information center 62 to the personal computer 61is recorded in the hard disk of the recording device 74 is the same asthat of the third exemplary embodiment, a description thereof isomitted.

FIG. 20 is a diagram showing the sub-routine of partial compressionprocessing according to the eighth exemplary embodiment of the presentinvention. FIG. 21 is a flow chart showing the operation of thenavigation device according to the eighth exemplary embodiment of thepresent invention.

In this case, in the personal computer 61 (FIG. 1) the CPU 71 executespartial compression processing to read out route guidance dataindicating information for route guidance from the hard disk and dividethe route guidance data into surrounding data and non-surrounding data(step S33-11). The non-surrounding data is further divided intoroute-surrounding data and other non-route-surrounding data.Subsequently, the route-surrounding data is compressed at thecompression rate α2 (step S33-14), and the non-route-surrounding data iscompressed at the compression rate α3 (step S33-15) to create partiallycompressed data supplied with an administration header thereby creatingpartially compressed data.

When the partially compressed data is created in this way, the CPU 71can transfer the partially compressed data to the navigation device 14.Thus, if an operator starts the navigation device 14 by operating theoperating section 73, CPU 71 executes navigation device startprocessing, in which the navigation device 14 starts up. Subsequently,the CPU 71 executes data transfer processing to read out the partiallycompressed data from the hard disk of the recording device 74 andtransmit it to the navigation device 14. In the navigation device 14,the CPU 31 (FIG. 2) executes partially compressed data recordingprocessing to record the partially compressed data into the flash memory30.

Once all of the partially compressed data is recorded in the flashmemory 30, the CPU 71 executes navigation device stop processing to stopthe navigation device 14. The partially compressed data is now availablefor route guidance.

Although according to this embodiment, the route guidance data iscompressed at the compression rate α2 for the route-surrounding datawhile for the non-route-surrounding data, is compressed at thecompression rate α3, alternatively the route guidance data may becompressed at other compression rates, for example, theroute-surrounding data may be compressed at compression rate α1 which islower than the compression rate α2 and the non-route-surrounding datamay be compressed at the compression rate α2 which is lower than thecompression rate α3.

Next, the operation of the navigation device 14 when a vehicle is drivenwill be described. First, if the ignition switch of a vehicle is turnedon, the navigation device 14 starts (step S91), so that a currentposition is detected by the GPS 21 and the direction of the vehicle isdetected based on a turning angle of the vehicle detected by the gyrosensor 26.

The CPU 31 executes route guidance processing so as to read out thepartially compressed data from the flash memory 30, and forms a mapscreen on a display of the display section 35 based on thenon-compressed surrounding data of the partially compressed data. TheCPU 31 displays a current position, a map of a surrounding region andthe direction of the vehicle on the map screen, displays a search routein the surrounding region of the current position, and notifies a driverof the search route with audio through a message from the audio outputsection in order to execute route guidance (step S92).

When the route guidance starts up in this way, the CPU 31 executesroute-surrounding data decompression processing in which it decompressesthe compressed route-surrounding data and then records theroute-surrounding data into the hard disk of the data recording section16 (step S93). Then, the CPU 31 determines whether or not allroute-surrounding data is decompressed (step S94).

If all route-surrounding data is decompressed, the CPU 31 executes offroute determination processing to read a current position and determineswhether the vehicle is off of the route based on the current positionand route data (step S95). If the vehicle is off of the route, the CPU31 executes non-route-surrounding data decompression processing in whichit decompresses the non-route-surrounding data and records thenon-route-surrounding data, which is the decompressed data, into thehard disk of the data recording section 16 (step S96).

The non-route-surrounding data decompression processing is executedgiving preference to those areas most likely to be used for a re-search(i.e., areas closest to route and/or current location).

The CPU 31 executes re-search processing, in which it determines whetheror not all the non-route-surrounding data is decompressed (step S97),and if all the non-route-surrounding data is decompressed, a currentposition and non-route-surrounding data are read and then, a route fromthe current position up to the original search route is re-searchedaccording to the non-route-surrounding data.

Because according to this exemplary embodiment the surrounding data isread immediately without decompression processing after the ignitionswitch is turned on to start the navigation device 14, a vehicle can bedriven immediately using the route guidance data.

Furthermore, according to this exemplary embodiment, the compressionprocessing is carried out by the personal computer 61, according tovarious other exemplary embodiments, the compression processing may beexecuted by the information center 62. In this case, in the compressionprocessing in the information center 62, the route guidance data isdivided into surrounding data and non-surrounding data, and thenon-surrounding data is further divided into route-surrounding data andother non-route-surrounding data. The surrounding data is not compressedwhile the route-surrounding data and non-route-surrounding data arecompressed at the compression rates α2, α3 respectively.

According to the seventh and eighth embodiments, after the compresseddata, partially compressed data, and the like transmitted from theinformation center 62 are downloaded into the hard disk of the personalcomputer 61, the compressed data, partially compressed data, and thelike are transferred to the navigation device 14. However, according tovarious other exemplary embodiments, the compressed data transmittedfrom the information center 62 may be received directly by thenavigation device 14.

According to the above-described exemplary embodiments, the compresseddata, partially compressed data, and the like downloaded into the harddisk of the recording unit 74 are transmitted to the navigation device14 and recorded in the flash memory 30. According to this exemplaryembodiment, the compressed data, partially compressed data, and the likedownloaded into the hard disk of the recording unit 74 are recorded intoa memory card temporarily and the memory card is set into the datarecording section 16 of the navigation device 14 and at the same time,recorded into the hard disk or the like of the data recording section16.

According to the above exemplary embodiments, the route guidance data istransmitted to the personal computer 61, the navigation device 14, andthe like as navigation information. However, if the route search is notexecuted, the map data can be transmitted to the personal computer 61,the navigation device 14 and the like as the navigation information. Inthis case, the map data is compressed.

According to the above exemplary embodiments, the compressed datatransmitted from the personal computer 61 or from the server 63 isrecorded in the flash memory 30 and after that, decompressed andrecorded in the hard disk of the data recording section 16 asdecompressed data. However, the compressed data transmitted from thepersonal computer 61 or from the server 63 may be recorded in the harddisk and the decompressed data may be recorded in the flash memory 30.Because as described above, the data recording section 16 allows variouskinds of external memory devices such as the memory card to be set aswell as the hard disk, the compressed data transmitted from the personalcomputer 61 or from the server 63 may also be recorded in an externalmemory device and the decompressed data may be recorded in the flashmemory 30.

As described above, the information center 62 is capable of transmittingroute guidance data and other types of information, such as trafficinformation, general information, image information, music informationand the like to the personal computer 61. Thus, an operator can transferother types of information downloaded into the hard disk to thenavigation device 14 when a vehicle stays in a garage and record it in,for example, the flash memory 30 in the navigation processing section17.

If communication required time for transferring the other types ofinformation to the navigation device 14 is long, the navigation device14 needs to be on. Thus, as described above, electric power consumed bythe navigation device 14 increases and consequently the load applied tothe battery mounted on a vehicle increases tremendously.

Accordingly, a ninth exemplary embodiment in which other types ofinformation may be transmitted from the information center 62 andcompressed to create compressed data and the compressed data istransferred to the navigation device 14 will be described.

FIG. 22 is a main flow chart showing the operation of a personalcomputer according to the ninth exemplary embodiment of the invention.FIG. 23 is a diagram showing the sub-routine of the compressionprocessing according to the ninth exemplary embodiment of the invention.FIG. 24 is a diagram showing the data structure upon decompressionprocessing according to the ninth exemplary embodiment of the invention.

First, if an operator transmits an information request to theinformation center 62 by operating the operating section 73 of thepersonal computer 61 (FIG. 1) the server 63 executes informationobtainment processing to read general information from a databasedisposed separately from the navigation database 64 and obtain it.

Subsequently, the server 63 executes information transmission processingto transmit general information obtained by the server 63 to thepersonal computer 61.

Then, in the personal computer 61, the CPU 71 executes receptionprocessing to receive the general information and the CPU 71 executesrecording processing to download the general information into the harddisk of the recording unit 74 (step S101).

After the navigation device 14 starts, the general information isclassified depending on whether a user needs it, that is whether itshould be provided and/or with what priority. Therefore, when thegeneral information is recorded in the hard disk, the priority order isrecorded together.

Next, the CPU 71 reads the memory capacity of the flash memory 30 (FIG.2) in the navigation device 14 (step S102), and the CPU 71 executescompression processing to compress the downloaded general informationbased on the memory capacity so as to be recorded in the flash memory 30(step S103).

Thus, the CPU 71 reads out the general information from the hard diskand divides the general information into data groups according to thepriority order (S103-1). The CPU 71 divides the general information intoa high priority data group to be decompressed with the highest priority,a medium priority data group to be decompressed with a next highestpriority, and a low priority data group to be decompressed with thelowest priority.

Subsequently, the CPU 71 compresses the high priority data, mediumpriority data and low priority data at the compression rates α1-α3(steps S103-4, S103-5, and S103-6) to create compressed data suppliedwith an administration header and records each compressed data into theflash memory of the recording unit 74. In this case, the respectivecompression rates α1-α3 of the high priority data, medium priority dataand low priority data are set to be different from each other. Thecompression rate al of the high priority data is set low because itneeds to be decompressed in the navigation device 14 immediately afterthe ignition switch is turned on. The compression rate α2 of the mediumpriority data is set to a medium level because it only needs to bedecompressed, for example, after a vehicle is started, and thecompression rate α3 of the low priority data is set high because it onlyneeds to be decompressed after the decompression of the medium prioritydata is terminated after the vehicle is started.

The administration header is information for controlling the compresseddata and includes, for example, an administration ID, data sizeindicating the size of the compressed data, and other data. Typically,due to the different compression rates, the data size of the compressedhigh priority data is large, the compressed medium priority data ismedium, and the compressed low priority data is small.

The CPU 71 executes data size determination processing to determine thedata size of the high priority data, medium priority data and lowpriority data, that is total data size in order to determine whether ornot the all data size is larger than the memory capacity of the flashmemory 30 (step S103-7). If the all data size is larger than the memorycapacity of the flash memory 30, the data size determination processingmeans changes the compression rates α1-α3 to higher values in order torecompress the data (step S103-8).

Although according to this exemplary embodiment, the high priority datais compressed at compression rate α1, according to various otherexemplary embodiments, the high priority data may not be compressed.

Although according to this embodiment, when the entire data size islarger than the memory capacity of the flash memory 30, the data sizedetermination processing means changes the compression rates α1-α3 tohigher values, in various other exemplary embodiments, only one or twoof the compression rates will be heightened if the entire data size islarger than the memory capacity of the flash memory 30.

If the compressed data is created in this way, the CPU 71 executescompressed data transmission processing to transfer the compressed datato the navigation device 14. Thus, if an operator starts the navigationdevice 14 by operating the operating section 73, the CPU 71 executesnavigation device start processing to turn on the power of thenavigation device 14 to start the navigation device 14 (step S104). TheCPU 71 executes data transferring processing to read out compressed datafrom the flash memory of the recording unit 74 and transfer it to thenavigation device 14 (step S105). Then, in the navigation device 14, theCPU 31 executes compressed data recording processing to recordcompressed data into the flash memory 30.

If all the compressed data is recorded in the flash memory 30, the CPU71 executes navigation device stop processing to stop the navigationdevice 14 (step S106) and the compressed data is available.

Thus, when general information is transmitted from the personal computer61 to the navigation device 14, the general information is compressedaccording to priority order. Therefore, the data size of the compresseddata can be reduced. Required communication time is also shortened and atime in which the navigation device 14 is powered may be reduced. Thus,power consumed by the navigation device 14 is decreased, andconsequently, load applied to a battery mounted on a vehicle can bereduced. Further, because the communication required time is short, anoperator's workload can be simplified thereby reducing communicationcost.

Although according to the above-described respective embodiments, apersonal computer 61 may be used as a user terminal and informationobtainment processing, compression processing, compressed datatransmission processing and the like are executed by the personalcomputer 61, it is possible to use a home server provided in a driver'shome as a user terminal and execute the information obtainmentprocessing, compression processing, compressed data transmissionprocessing and the like at the home server.

In this case, the home server refers to a server which obtainsinformation from outside, accumulates the obtained information andcontrols and edits the accumulated information corresponding to a user'srequest and further is capable of transmitting information to anexternal device, for example, a personal computer, portable phone, PDA,navigation device and the like.

While various features of this invention have been described inconjunction with the exemplary embodiments outlined above, variousalternatives, modifications, variations, and/or improvements of thosefeatures may be possible. Accordingly, the exemplary embodiments of theinvention, as set forth above, are intended to be illustrative. Variouschanges may be made without departing from the spirit and scope of theinvention.

1-33. (Canceled)
 34. A navigation system, comprising: a controller thatcompresses at least one of a plurality of information portions, each oneof the plurality of information portions having a priority, wherein eachof the at least one of the plurality of information portions iscompressed based on its priority; and a transmitter that transmits theat least one compressed information portion to a navigation device. 35.The navigation system of claim 34, wherein the controller and thetransmitter are included in an information center.
 36. The navigationsystem of claim 34, wherein the controller and the transmitter areincluded in a user terminal.
 37. The navigation system of claim 36,wherein the user terminal is connected to an information center over anetwork.
 38. The navigation system of claim 37, wherein the informationcenter provides the plurality of information portions to the controllerin the user terminal.
 39. The navigation system of claim 34, whereineach of the at least one of the plurality of information portions isdecompressed in the navigation device based on its priority and acompression rate for each of the at least one information portions isrelated to the priority.
 40. The navigation system of claim 34, whereinthe plurality of information portions comprises a surroundinginformation portion including navigation data surrounding an areacontaining a starting point and a non-surrounding information portionincluding other navigation data, and the controller compresses at leastthe non-surrounding information portion.
 41. The navigation system ofclaim 40, wherein the controller compresses the surrounding informationportion and the non-surrounding information portion.
 42. The navigationsystem of claim 40, wherein the non-surrounding information portionincludes a plurality of information sub-portions.
 43. The navigationsystem of claim 42, wherein the non-surrounding information portionincludes at least a route-surrounding information sub-portion and anon-route-surrounding information sub-portion.
 44. The navigation systemof claim 43, wherein the controller compresses at least one of thesurrounding information portion, the route-surrounding informationsub-portion, and the non-route-surrounding information sub-portion, atrespectively different compression rates.
 45. The navigation system ofclaim 44, wherein a compression rate of the non-route-surroundinginformation sub-portion is higher than a compression rate of theroute-surrounding information sub-portion and a compression rate of theroute-surrounding information sub-portion is higher than the surroundinginformation portion.
 46. The navigation system of claim 34, wherein eachof the plurality of information portions includes map data.
 47. Thenavigation system of claim 34, wherein at least one of the plurality ofinformation portions includes route guidance data including a searchedfor route.
 48. A navigation device, comprising: a receiver that receivesat least one of a plurality of information portions, each one of theplurality of information portions having a priority, wherein each of theat least one of the plurality of information portions is compressedbased on its priority.
 49. The navigation device of claim 48, furthercomprising: a controller that decompresses each of the at least onecompressed information portions based on its priority.
 50. Thenavigation device of claim 48, wherein a compression rate for each ofthe at least one information portions is related to its priority. 51.The navigation device of claim 48, wherein the plurality of informationportions comprises a surrounding information portion includingnavigation data surrounding an area containing a starting point and anon-surrounding information portion including other navigation data. 52.The navigation device of claim 51, wherein the non-surroundinginformation portion includes a plurality of information sub-portions.53. The navigation device of claim 51, wherein the controllerdecompresses the surrounding information portion before thenon-surrounding information portion.
 54. The navigation device of claim53, wherein, when an ignition switch is turned on, the controller firstdecompresses the surrounding information portion and second decompressesthe non-surrounding information portion.
 55. The navigation device ofclaim 54, wherein the controller decompresses the non-surroundinginformation portion after a vehicle starts traveling.
 56. The navigationdevice of claim 53, wherein the controller decompresses the surroundinginformation portion as soon as it is received by the receiver anddecompresses the non-surrounding information portion when an ignitionswitch of a vehicle is turned on.
 57. The navigation device of claim 51,further comprising a present position detector that detects a currentposition, wherein the controller determines whether each of theplurality of information portions is the surrounding information portionbased on position information included within each of the plurality ofinformation portions and the current position.
 58. The navigation deviceof claim 51, further comprising a present position detector that detectsa current position, wherein the controller determines whether each ofthe plurality of information portions is nearby non-surroundinginformation based on position information included within each of theplurality of information portions and the current position and thecontroller successively decompresses nearby non-surrounding data as thecurrent position is updated.
 59. The navigation device of claim 52,wherein the non-surrounding information portion includes at least aroute-surrounding information sub-portion and a non-route-surroundinginformation sub-portion.
 60. The navigation device of claim 59, wherein,when an ignition switch is turned on, the second controller firstdecompresses the surrounding information portion, second decompressesthe route-surrounding information sub-portion, and third decompressesthe non-route-surrounding information sub-portion.
 61. The navigationdevice of claim 48, wherein each of the plurality of informationportions includes map data.
 62. The navigation device of claim 48,wherein at least one of the plurality of information portions includesroute guidance data including a searched for route.
 63. A method fortransmitting information to a navigation device, comprising: compressingat least one of a plurality of information portions, each one of theplurality of information portions having a priority, wherein each of theat least one of the plurality of information portions is compressedbased on its priority; and transmitting the at least one compressedinformation portion to the navigation device.
 64. The navigation deviceof claim 48, wherein a compression rate for each of the at least oneinformation portions is related to its priority.
 65. A method forreceiving information in a navigation device, comprising: receiving atleast one of a plurality of information portions, each one of theplurality of information portions having a priority, wherein each of theat least one of the plurality of information portions is compressedbased on its priority.
 66. The method of claim 65, further comprising:decompressing each of the at least one compressed information portions,wherein each of the at least one of the plurality of informationportions is decompressed based on its priority.
 67. The navigationdevice of claim 48, wherein a compression rate for each of the at leastone information portions is related to its priority.
 68. A navigationsystem, comprising: a first controller that compresses at least one of aplurality of information portions, each one of the plurality ofinformation portions having a priority, wherein each of the at least oneof the plurality of information portions is compressed based on itspriority; a transmitter that transmits the at least one compressedinformation portion to a navigation device; a receiver that receives theat least one compressed information portion; and a second controllerthat decompresses each of the at least one compressed informationportions based on its priority.
 69. The navigation system of claim 68,wherein the receiver is in the navigation device.
 70. The navigationsystem of claim 69, wherein the second controller is in a navigationdevice.
 71. The navigation system of claim 68, wherein the firstcontroller and the transmitter are included in an information center.72. The navigation system of claim 68, wherein the first controller andthe transmitter are included in a user terminal.
 73. The navigationsystem of claim 72, wherein the user terminal is connected to aninformation center over a network.
 74. The navigation system of claim68, wherein the plurality of information portions comprises asurrounding information portion including navigation data surrounding anarea containing a starting point and a non-surrounding informationportion including other navigation data, and the first controllercompresses at least the non-surrounding information portion.
 75. Thenavigation system of claim 74, wherein the first controller compressesthe surrounding information portion and the second controllerdecompresses the surrounding information portion before thenon-surrounding information portion.
 76. The navigation system of claim68, wherein each of the plurality of information portions includes mapdata.
 77. The navigation system of claim 68, wherein at least one of theplurality of information portions includes route guidance data includinga searched for route.
 78. The navigation system of claim 68, wherein acompression rate for each of the at least one information portions isrelated to the priority.